Generally, an object is measured by using a microscope. For example, it becomes possible to analyze portions of a part from an infrared spectrum of the part measured by using the microscope.
To obtain the optical data from the object, it is necessary to gather a reflected light from the object or a transmitted light by the object.
However, it is very difficult to apply a prior art technique to gather the reflected light or the transmitted light of the object when the object of measurement is such as a surface of macromolecule film or semiconductor, or materials which strongly absorb light such as an aqueous solution which absorbs the infrared light.
From this reason, a total reflection measuring method is applied to an object where it is difficult to measure the reflected light or the transmitted light from the object.
The principle of the total reflection measuring method is explained with reference to FIGS. 5A and 5B.
An ATR hemisphere prism 12 or ATR triangle pole prism 12 having a refractive index bigger than that of the object 10 is placed on the object 10, and a beam of light having a wavelength .lambda. is entered into the prism 12.
When the angle of incidence from the prism 12 to the object 10 is bigger than the critical angle, the light is totally reflected at the critical surface between the object 10 and the prism 12. At this reflection point, the beam of light enters the sample a little. The entering depth d.sub.p is represented by the following formula (1): EQU d.sub.p =.lambda./[2.pi.n.sub.1 {sin.sup.2 .theta.-(n.sub.2 /n.sub.1).sup.2 }.sup.1/2] ( 1)
wherein d.sub.p represents an entering depth that the light strength decreasing to i/e, and .lambda. represents the wavelength of the light.
Therefore, the totally reflected light decreases according to the absorption of the light at the critical surface. As a result, it becomes possible to obtain optical information from the object of measurement by analyzing characteristics of the total reflection light at the critical surface between the object and the prism, even if the object is a surface such as a macromolecule film or a semiconductor, or materials which strongly absorb the light.
However, when applying a conventional total reflection measuring apparatus to the general micro measuring apparatus, it is necessary to observe the measured part of the object by visual observation in visible light. The object has to be placed on a total reflection measuring apparatus, the total reflection measuring apparatus has to be connected to the micro measuring apparatus to obtain the optical information. As mentioned above, it required a very complex operation. Further, the improvement of the measurement precision was limited.